Here are some responses. I'm not altogether sure about the right
answer. According to textbooks, "invertase" converts sucrose to
glucose+fructose. So the web site mentioned below is not quite correct
- either the corn syrup's ***sucrose*** is broken down as above or the
***glucose*** that results from the hydrolysis of starch is then
converted to fructose. The word "invertase" comes from the fact that
the optical rotation of sucrose is opposite that of the products. I
don't know if the same thing happens when glucose is converted to fructose.
****Try this web site.
http://food.oregonstate.edu/sugar/hfcs.html
They mention an invertase to convert glucose to fructose. It should be
an isomerase!
*****Thirty or so years ago, invertase was immobilized on columns
through which glucose-rich corn syryp was passed. The product was HFCS.
Biochemists at Corn Products (Argo, IL) patented the technology, but
probably other patents were obtained by others.
****It's made by "cooking" corn starch to break down the starch to
glucose. My impression is that some of the glucose is then converted
enzymatically to fructose. Product specifications available on the web
indicate that it does contain about 50% of its sugars as glucose. I
imagine that it's used more because its sweeter. It also gives a
moister product in baked goods. (The cynic in me suggests that maybe
it's also used so that sugar doesn't have to be the main ingredient on
the list, thus not scaring away some calorie-conscious consumersl.)
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